This invention relates to a method for making an apertured nonwoven fabric containing thermoplastic synthetic microfibers and being suitable to be used as a liquid-permeable topsheet in disposable body fluids absorbent articles such as disposable diapers or sanitary napkins.
It is known to form a nonwoven fabric comprising the thermoplastic synthetic fibers having a fineness of 1.about.10 d with liquid-permeable apertures so as to be used as a topsheet in a body fluids absorbent article. An example of the methods for such nonwoven fabric is disclosed in Japanese Patent Application Disclosure Gazettes (Kokai) Nos. Sho 61-176346 and Sho 62-69867, according to which a card web comprising fibers each having a fineness of 1.about.10 d and a length of approximately 50 mm is subjected to high velocity water jet streams to form a nonwoven fabric. During this processing by the water jet streams, component fibers of a web are partially reoriented around a plurality of projections formed on a surface of support for the web and thereby the nonwoven fabric is formed with a plurality of liquid-permeable apertures corresponding to the respective projections. It is also known to form these liquid-permeable apertures by feeding the nonwoven fabric to a pair of embossing rolls so that the nonwoven fabric may be pierced by a plurality of needle teeth formed on a peripheral surface of one of these embossing rolls.
However, the conventional method for forming the liquid-permeable topsheet with these apertures is often accompanied with an inconvenience such that, when it is attempted to form the apertures each having a diameter of 0.5.about.5 mm, individual fibers may often extend from the aperture periphery into this aperture, resulting in the indistinctly contoured aperture. Probably, it is for the reason that the individual fibers can not be smoothly reoriented around each of projections. The smaller a diameter of the aperture and/or larger a basis weight of the nonwoven fabric is, the greater this problem becomes serious. While it is obvious that the individual fibers extending into the aperture lead to a substantial reduction of the aperture's diameter, a degree of such reduction is not necessarily uniform. This makes a proper design of the aperture difficult. Accordingly, it is required for the nonwoven fabric used as the liquid-permeable topsheet to have a sufficiently high formability to facilitate formation of the apertures.